Electronic transmission control system for a bicycle

ABSTRACT

An electro-mechanical system for shifting gears on a multi-gear bicycle or other human-powered vehicle includes a closed loop derailleur position control system using a circuitry for measuring derailleur position. Shifting gears is accomplished automatically based on rider cadence or manually using signals supplied by hand operated switches. The system calculates gear ratios based on bicycle speed and cadence and then sorts the gear ratio in order from lowest to highest. During automatic operation, the system calculates a cadence from bicycle speed and gear ratio, determines if the calculated cadence is within predetermined limits set by the rider, and it changes the gear ratio if the calculated cadence is not within the predetermined limits. The system has additional modes of operation which include calibration modes for calibrating the positions of the front and rear derailleurs for each gear, as well as a semi-automatic mode in which the system calculates the cadence from the bicycle speed and gear ratio, and signals the rider to upshift or downshift if the cadence is outside of the predetermined limits selected by the rider. The electronic bicycle transmission control system of the present invention is retrofittable to a wide range of conventional multi-gear bicycles.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of bicycles and bicycle control systems used for controlling the transmission of rotational torque generated by a rider to the driving wheel or wheels. More particularly, the present invention relates to a retrofittable, electronic, fully automatic gear shifting control system for multi-gear bicycles.

2. Discussion of the Prior Art

Bicycling is most efficient when the rider maintains a constant number of crank revolutions per minute in spite of changing bicycle speed or changing terrain over which the bicycle is traveling. As used herein, a term "cadence" means the number of crank revolutions per minute or any other cyclic measurement of the rider's activity. A rider generally desires to maintain a cadence that is appropriate for his or her level of physical ability.

In conventional multi-gear bicycles, such as those of a "ten-speed" type, the rider manually changes gears as a function of bicycle speed and difficulty of terrain in order to maintain a comfortable/target cadence. To accomplish this, however, a rider must continuously ascertain what his or her current cadence is and then shift gears as appropriate in order to maintain the preferred cadence. This can be a very subjective process which, as a consequence, is inefficient and imprecise. The rider has to consciously keep track of his or her cadence and shift appropriately, which may be distracting and may adversely affect rider safety. For example, many cyclists do not even know which way to move the shift levers on a multi-gear bicycle in order to increase or decrease their cadence, while some riders find it is difficult to maintain their balance while trying to shift gears because of the requirement of steering with one hand while moving the shift lever(s) with the other hand. In addition, on multi-gear bicycles, the rider must make a small adjustment to the position of the front derailleur whenever the rear derailleur position is changed in order to compensate for the varying chain angle between the rear sprockets and the front chainrings as different gears are selected.

Several prior art systems have been used which attempt to automate the task of shifting the gears. One example of prior art automatic gear shifting systems is the Bike-O-Matic transmission manufactured by Bike-O-Matic, Ltd., of Eagleville, Pennsylvania. In the Bike-O-Matic system, tension placed on the chain due to the rider's pedal effort is used to control shifting. High chain tension causes the derailleur to shift the gears into a lower gear while lower chain tension causes the derailleur to shift the gears into a higher gear. Shifting into a lower gear effectively increases the rider's cadence, while shifting into a higher gear effectively decreases the rider's cadence. One problem with the Bike-O-Matic transmission is that it is a mechanical system that relies on chain tension. During the transition from one gear to another, there is a relatively slow actuation of the derailleur. This slow actuation results in excessive friction caused by rubbing between the chain, derailleur, and sprockets which decreases the rider s efficiency. In addition, when a shift occurs, the mechanism does not position the derailleur in line with sprockets as in the case of manual shifting. The system moves the derailleur continuously rather than discreetly as a function of chain tension. Consequently, the position at which the derailleur stops for a given amount of chain tension may not in fact line up with a particular sprocket on the bicycle.

Furthermore, since the Bike-O-Matic system relies on chain tension, it doesn't help the rider to maintain his or her preferred cadence. For example, on bicycles with multiple front chain rings of different sizes, much greater pedal force would be required to maintain the same chain tension when the rider is using a larger chainring as compared to a smaller chainring. This is because the moment arm of the larger chainring is greater. Using chain tension to control gear shifting can cause shifting at inopportune times, so there could in fact be times when the system will shift gears when the rider does not desire to do so.

Another example of prior art automatic bicycle transmissions is the Browning Electronic Acushift Transmission, manufactured by SunTour. The Browning Transmission electrically shifts the chain using hinged chainring sections. One limitation of the Browning Transmission is that it is designed for use only on the front chainrings of a bicycle. In addition, the Browning Transmission does not use a derailleur, but rather uses a special set of chainrings and electrical controls. Consequently, it is difficult to retrofit this system onto multi-gear bicycles which use conventional derailleurs and chainrings.

Therefore, an object of the present invention is to provide a control system for a human-powered vehicle, such as a bicycle that controls gear shifting so as to maintain a cadence within user-selected limits.

Another object of the invention is to provide a control system for a bicycle that maintains a cadence within user-selected limits over a wide range of bicycle speeds and bicycle gear ratios.

Another object of the present invention is to provide a control system for a bicycle that controls gear shifting automatically so as to maintain a cadence within user-selected limits thereby enhancing rider efficiency and safety.

A further object of the invention is to provide a control system for a bicycle that controls gear shifting automatically and that is retrofittable to a wide range of conventional multi-gear bicycles which use conventional gear shifting systems.

SUMMARY OF THE INVENTION

The foregoing and other objects, features, and advantages of the present invention are achieved in a retrofittable electronic control system for a human-powered vehicle such as a bicycle. The system can operate in a manual, semi-automatic, or fully automatic mode, and can be installed on any conventional bicycle frame. All bicycles include means for transmitting rotational torque generated by a rider to at least one wheel. The means for transmitting power includes, for example, the front chainrings, the chain itself, and the rear sprockets on the bicycle. The invention includes a means for adjusting the transmitting means in order to change gear ratios on the bicycle. In a preferred embodiment, the adjusting means includes actuators and shift arms which cooperate to deflect the bicycle s shift cables from their normal rest position to effect gear changing. The invention further includes a data processor, which may be a microprocessor or the like. In the manual mode of operation, the data processor has previously stored the correct positions for the shift arms for each gear on the bicycle. The rider uses handlebar switches to instruct the data processor to perform a gear shift. In response to signals from the data processor, the actuators and shift arms move the front and rear derailleur shift cables as required to shift gears. Position sensors detect the position of the shift arms and provide a feedback signal to the data processor indicating the current position of the derailleurs. The invention thus provides closed loop control of the positions of the front and rear derailleurs.

In the fully automatic mode of operation, the data processor calculates a cadence from the bicycle's current speed and gear ratio. The system continuously compares the calculated cadence with a set of predetermined cadence limits selected by the rider and determines whether or not the calculated cadence is too high or too low. If the calculated cadence is too low, and the rider is pedaling, the system adjusts the transmitting means, using the actuators and shift arms to move the front and rear derailleurs using closed loop control of the derailleur positions to downshift to the next lower gear. Downshifting increases the gear ratio, which increases the rider's cadence. If, on the other hand, the system determines that the calculated cadence is too high, and the rider is pedaling, the system will upshift to the next higher gear, using the actuators and shift arms to move the derailleurs using closed loop control via the bicycle's shift cables. Upshifting decreases the gear ratio, which decreases the rider's cadence.

The system has additional modes of operation which include calibration modes for calibrating the positions of the front and rear derailleurs for each gear, including multiple positions per chainring for the front derailleur, in order to compensate for the Varying chain angle between the front chainrings and the rear sprockets as different gears are selected. A semi-automatic mode of operation is also provided, in which the system calculates the theoretical cadence from the current bicycle speed and gear ratio, and signals the rider to upshift or downshift if the calculated cadence is outside the predetermined limits selected by the rider.

The foregoing and other objects, features, and advantages of the present invention will be more readily understood and apparent from the following detailed description of the invention, which should be read in conjunction with the accompanying drawings, and from the claims which are appended at the end of the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a side view of a bicycle with the electronic control system of the present invention installed thereon;

FIG. 1A is a partial end view taken in the direction of line 1A--1A in FIG. 1 illustrating the motion of the rear derailleur during gear changing operations.

FIG. 2 is a side view of the bicycle and transmission control system of FIG. 1 in greater detail;

FIG. 3 is a perspective view of the bicycle and electronic transmission control system of FIG. 1;

FIG. 4 is a perspective view of the bicycle and electronic transmission control system of FIG. 3 in greater detail;

FIG. 5 is a cross-sectional view taken along the line 2--2 in FIGS. 1 and 2 showing the shift arms and gear position sensors used in the bicycle transmission control system of FIG. 1;

FIG. 6 is a plan view of the control module used in the bicycle transmission control system of FIG. 1;

FIG. 7 is a flow chart illustrating the processing steps carried out by the electronic bicycle transmission control system of FIG. 1 in the front derailleur calibration mode;

FIG. 8 is a flow chart illustrating the processing steps carried out by the electronic bicycle transmission control system of FIG. 1 in the rear derailleur calibration mode;

FIG. 9 is a flow chart illustrating the processing steps carried out by the electronic bicycle transmission control system of FIG. 1 in the semi-automatic mode; and

FIG. 10 is a flow chart illustrating the processing steps carried out by the electronic bicycle transmission control system of FIG. 1 in the fully automatic mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of illustration only, and not to limit generality, the present invention will now be explained with reference to its use on a "ten-speed" type of bicycle. However, one skilled in the art will recognize that the present invention is applicable to and can be retrofitted on a wide variety of multi-gear bicycles as well as a variety of human-powered vehicles.

Reference is now made to FIGS. 1-6, which figures illustrate the electronic bicycle transmission control system of the present invention installed or retrofitted onto a conventional ten-speed bicycle 20. A typical bicycle 20 includes a frame 300 having a head tube 302, a down tube 18, a seat tube 40, seat stays 304 and chainstays 306. A seat 308 is attached to the distal end of seat tube 40. A handlebar 80 is mounted onto head tube 302. A front wheel 310 is rotatably mounted to front forks 312, which are in turn connected to handlebar 80 through head tube 302. A rear wheel 314 is rotatably mounted to seat stays 304 and chainstays 306. The bicycle 20 additionally includes rear sprockets 316, rear derailleur 318, front chainrings 320, front derailleur 321, cranks and pedals 322, and a chain 324 for transmitting torque qenerated by the rider from the front chainrings 320 to the rear sprockets 316. For clarity, these conventional components have been omitted from FIGS. 2-6, but one skilled in the art will realize that they are obviously a part of the bicycle 20.

The control system of the present invention which is retrofitted onto bicycle 20 includes shift arms 10 and 12 which are used to move the rear and front derailleurs, respectively. Shift arms 10 and 12 pivot about shift arm position sensors 14 and 16 that are in turn clamped to the down tube 18 of the bicycle 20. Actuators 22, 24 are connected respectively to shift arms 10 and 12 for changing the position of shift arms 10 and 12 to effectuate the gear changing operation.

The present invention additionally includes a cadence sensor 26, which senses the rider's actual cadence. Cadence sensor 26 may be one of a variety of commercially available types, such as a magnetic, optical, or mechanical type sensor. A preferred sensor is one which employs a magnetic reed switch. This type of sensor uses a magnet mounted to one of the bicycle cranks and a switching element mounted to the bicycle frame. During each revolution of the crank, the magnet passes by the switching element causing a digital pulse to be generated. The invention also includes a wheel sensor 28 which is used to sense the speed of rotation (revolutions per minute or RPM) of the driving wheel 30 (and therefore the speed) of the bicycle. Wheel sensor 28 may be one of a variety of commercially available types, such as a magnetic, optical, or mechanical type sensor. A preferred sensor is one which employs a magnetic reed switch and operates in the same manner as the cadence sensor.

Data supplied by wheel sensor 28, cadence sensor 26, and gear position sensors 14, 16 are supplied to a data processing unit 32 which performs computations to determine cadence, alerts the rider when a gear shift is appropriate, and performs various other control functions to be discussed in greater detail hereinafter. Data processing unit 32 additionally receives inputs from handlebar switches 34 and 36 which the rider uses during calibration and to instruct the system to perform a gear upshift or a gear downshift. Handlebar switches 34 and 36 are conventional magnetic, optical, or mechanical type devices. A preferred switch is a mechanical momentary-action switch. Data processing unit 32 receives data from cadence sensor 26, wheel sensor 28, and handlebar switches 34, 36 over connections 27, 29, 35, and 37 respectively. These connections may be conventional wires, optical fibers, wireless transmit/receive means, or other means, depending on the type of switch or sensor used. Data processing unit 32 additionally sends control signals to actuators 22, 24 over connections 21, 23, which connections may be conventional wires, optical fibers, wireless transmit/receive means, or other appropriate means.

The retrofittability of the present invention is enhanced because the entire actuation and gear position sensing mechanism including actuators 22, 24, shift arms 10, 12, and position sensors 14, 16 is clamped to the bicycle frame at only two points. The ends of actuators 22, 24 are secured to the bicycle seat tube 40 by clamp 42 at pivot point 44. Position sensors 14, 16 are clamped to the down tube 18 using brackets 92, 94, as illustrated in FIG. 5, which may be clamped to the down tube 18 by using bolts which pass through holes drilled in bosses 96 and nuts to hold the bolts in place. Cadence sensor 26, wheel sensor 28, data processing unit 32, and handlebar switches 34, 36 may be easily attached to the bicycle 20 using conventional clamping means thereby providing for rapid installation of the present invention onto a conventional bicycle frame. One skilled in the art will appreciate that the present invention may be retrofitted onto a bicycle frame without dismantling or removing any major components of the bicycle.

Additionally, as shown particularly in FIGS. 3 and 4, actuators 22 and 24 are mounted substantially parallel to seat tube 40 and in close proximity to each other and the seat tube in order to eliminate any interference with the rider's legs during pedaling action. Actuators 22, 24 may be any electro-mechanical device that produces the motion in shift arms 10 and 12 which is required to effect rapid and precise gear changes.

In a preferred embodiment, actuators 22, 24 each include a motor which may be, for example, a DC gear motor, and a battery pack which supplies the necessary power for the motors. Actuators 22, 24 also include rotatable tubular portions 46, 48 which portions rotate clockwise or counterclockwise as driven by the motors housed inside actuators 22, 24. Two threaded shafts 50, 52 extend into the tubular rotatable portions 46, 48 which portions have interior threads that engage the threaded shafts 50, 52. Threaded shafts 50, 52 are connected to brackets 54, 56 and brackets 54, 56 are connected to shift arms 10, 12 at pivot point 58, 60. Shift arms 10 and 12 are configured to provide strength while at the same time eliminating any interference with the conventional operation of the cranks and chainrings of the bicycle. In a preferred embodiment, shift arms 10 and 12 are bellcranks formed of triangularly shaped planar pieces of a material such as aluminum or steel.

Shift control cables 62, 64 which control the position of the front and rear derailleurs (in the case of manual shifting by shift levers 358 mounted on the bicycle down tube or handlebars,) pass between shift arms 10, 12 and brackets 92 and 94 as shown in FIGS. 2 and 5 are in contact with actuation points 66, 68.

Position sensors 14, 16, as particularly illustrated in FIG. 5, are contained within brackets 92, 94. Shift cables 62, 64 pass over beveled cable guides 98, 100, respectively. Beveled cable guides 98, 100, position sensors 14, 16, and shift arm brackets 10, 12 are all coaxially disposed about pivot points 102, 104, respectively. Beveled cable guides 98, 100 are attached to brackets 92 and 94. Arms A14 and A16 are attached to shift arms 10, 12 and position sensors 14, 16 so that rotation of the shift arms 10, 12 causes position sensors 14, 16, to register the position of the shift arms 10 and 12 which in turn registers the position of the rear and front derailleurs of the bicycle. The position sensors 14, 16 may be one of a variety of commerically available optical or mechanical sensors such as encoders. In a preferred embodiment of the invention, the position sensors are potentiometers and shift arms 10, 12 are connected to the wiping arm of the potentiometers by arms A14 and A16. Varying resistance of the potentiometers as the shift arms 10, 12 are moved is used to sense rear and front derailleur positions. The position of shift arms 10, 12 (and the resulting position of the rear and front derailleurs) as sensed by position sensors 14, 16 is transmitted to data processing unit 32 for use in controlling bicycle gear shifting.

During operation of the electronic transmission control system, the actuators 22, 24, under control of data processing unit 32, rotate the tubular portions 46, 48 as the chuck of an electric drill is rotated, for example. As shown in FIG. 2, this rotation causes threaded shafts 50, 52 to be moved along the directions indicated by arrows 53A and 53B. The motion of the threaded shafts 50, 52 causes shift arms 10, 12 to move actuation points 66, 68 in an arc along line 72. Shift cables 62, 64 are therefore moved between their rest positions parallel to down tube 18 and the position indicated by dotted lines 74, 76. Shift cables 62, 64 are held against actuation points 66, 68 by return spring tension in the front and rear derailleurs.

Referring to FIG. 1A, there is shown partial end view taken in the direction of line 1--1 in FIG. 1. The rear sprockets include sprockets 316A-316E. Rear derailleur 318 includes pivot joints 360, 362, and 334. A return spring 350 provides spring tension that constantly urges derailleur 318 to a position where the derailleur gears 352 and 354 are in line with rear sprocket 316E. Rear derailleur 318 is effectively biased towards selecting gear 316E.

When tubular portion 46 is rotated so that threaded shaft 54 is moved along the direction of arrow 53B, shift arm 10 moves actuation point 66 in an arc along line 72 towards position 74 of shift cable 62. Since shift cable 62 is anchored at one end by the manual shift levers 358 on the bicycle, the movement of actuation point 66 pulls shift cable 62 in a direction indicated by arrow 62A. The other end of the shift cable 62 passes through shift cable housing 356 and is anchored to the rear derailleur at point 358. Therefore, as shift cable 62 is pulled by actuation point 66 in the direction of arrow 62A, rear derailleur 318 is moved along a direction indicated by arrow 318A to select one of the rear sprockets 316A-316D. This process can continue until actuation point 66 has moved shift cable 62 to the position indicated by dashed line 74 as particularly illustrated in FIG. 2. In this case, rear derailleur 318 is aligned with rear sprocket 316A. From this position, as threaded shaft 54 is moved in a direction along arrow 53A by the rotation of tubular portion 46, actuation point 66 is moved along arc 72 so that shift cable 62 moves along a direction indicated by arrow 62B as shown in FIG. 2. Return spring 350 therefore moves rear derailleur 318 along a direction indicted by arrow 318B as shown in FIG. 1A to move the chain 324 from rear sprocket 316A to one of the other rear sprockets 316D-316E.

The electronic transmission control system of the present invention stores the correct positions for the rear derailleur as programmed by the rider in data processing unit 32. The system only moves rear derailleur 318 in discreet increments equal to the lateral spacing between rear sprockets 316A-316E. Therefore, the chain doesn't get hung up between any of the rear sprockets, as can happen with various prior art systems. One skilled in the art will additionally appreciate that although the shifting operations have been explained with respect to their use in controlling the rear derailleur of a bicycle, a conventional front derailleur 321 as illustrated in FIG. 1, is controlled in the same manner using actuator 24, rotation portion 48, threaded shaft 56, shift arm 12, and actuation point 68, which act on shift cable 64. In addition, the front derailleur, like the rear derailleur, is only moved in discreet increments equal to the lateral spacing between the front chainrings. Consequently, as shift arms 10, 12 move along the arc defined by line 72, the shift cables 62, 64 control the position of the rear and front derailleurs, respectively, in order to select a particular gear ratio.

In a preferred embodiment of the invention, with manual mode selected, handlebar switch 34 is used to instruct the data processing unit 32 to upshift to the next higher gear in order to decrease the gear ratio (and decrease the rider s cadence) while handlebar switch 36 is used to instruct data processing unit 32 to downshift to the next lower gear in order to increase the gear ratio (and increase the rider's cadence). Each time handlebar switch 36 is activated by the rider, the system will downshift by one gear. Each time handle bar switch 34 is activated by the rider, the system will upshift by one gear.

Data processing unit 32 is clamped to handlebar 80 using bracket 84. As shown in FIG. 6, data processing unit 32 has various control switches which operate to control the electronic bicycle transmission control system. Data processing unit 32 contains a microprocessor, a memory for storing shifting programs as well as user entered data, and analog to digital converters for converting the data from position sensors 14, 16 into a form that can be processed by the microprocessor. Data processing unit 32 is also connected to and receives data from cadence sensor 26, wheel sensor 28, and handlebar switches 34, 36. Data processing unit 32 also contains a display 82 which may be, for example, a liquid crystal or vacuum fluorescent type of display. Display 82 is used to provide a visual indication to the rider of various parameters, such as the rider's cadence, the current gear ratio, current bicycle speed, elapsed time, etc.

Mode switch 86 is used to cycle data processing unit 32 through its various operational modes as selected by the rider. In a preferred embodiment of the invention, the electronic bicycle transmission control system has five operational modes: front calibration, rear calibration, manual, semi-automatic and fully automatic. The rider presses mode switch 86 to sequentially step through the five operational modes and select the particular mode of operation that is desired. Indicators 88, which may be, for example, light emitting diodes, provide a visual indication as to which operating mode has been selected. Set switch 90 is used to enter various parameters into the memory of data processing unit 32.

Overview of System Operation

The electronic bicycle transmission control system of the present invention can be easily retrofitted onto a variety of conventional multi-gear type of bicycles. Once the system has been installed on the rider's bicycle, the rider places the shift levers that would normally be used during conventional manual shifting of the bicycle gears against their respective stops so that they will not interfere with operation of the electronic transmission control system. Next, the rider performs a calibration of the transmission control system in which the data processing unit 32 stores the positions of the shift arms 10, 12 and the particular gear ratio associated with each stored position. Thereafter, the rider may choose from manual, semi-automatic, or fully automatic modes of operation. In the manual mode of operation, shifting will be left up solely to the discretion of the rider. The rider can choose an upshift by activating the right handlebar switch or a downshift by activating the left handlebar switch. In the semi-automatic mode, the system calculates the rider s theoretical cadence for the current gear ratio and bicycle speed and informs the rider, by audible or visual signals, that his or her cadence is outside the preprogrammed limits. The rider still has discretion to choose whether or not to shift the gears via the handlebar switches, as in the manual mode of operation.

In the fully automatic mode of operation, the system continuously calculates the rider s theoretical cadence for the current gear ratio and bicycle speed. The system then determines whether or not this calculated cadence is within the limits chosen by the rider. If the calculated cadence is too low, the system informs the rider, by audible or visual signal, then automatically shifts gears to the next lower gear (decreasing the gear ratio) in order to increase the rider's cadence. Conversely, if the calculated cadence is too high, the system informs the rider, by audible or visual signal, then automatically shifts gears to the next highest gear (increasing the gear ratio) in order to decrease the rider s cadence. In all operating modes, shifting will not occur if the rider is not pedaling. This will prevent derailleur damage. Thus, for all gear ratios and bicycle speeds, the system maintains the rider s cadence within preset limits thereby increasing overall rider efficiency and safety and relieving the rider of the need to manually shift gears.

Detailed Description of the Control Program

Reference is now made to FIG. 7, which figure illustrates the processing steps carried out by the system during the front derailleur calibration mode. In this mode, the rider stores the correct positions of the front derailleur for each gear position in the data processing unit s memory. In step 110, the system starts and proceeds to step 112 in which a check is made to determine whether or not the front derailleur calibration mode has been selected. If the answer is no in step 112, the system continues in step 112 until the front derailleur calibration mode is activated or some other mode of operation is selected by the rider. If, on the other hand, the answer is yes in step 112 indicating that the rider has selected the front derailleur calibration mode, the system proceeds to step 114.

In step 114, the system checks to determine whether or not the left handlebar switch 36 has been activated. If the answer is no in step 114, indicating that the left handlebar switch is not activated, the system proceeds to step 115. On the other hand, if the answer is yes in step 114, the system proceeds to step 114A. In step 114A, the system activates actuator 24 in order to adjust the position of shift arm 12 which consequently results in an adjustment to the position of the front derailleur. In step 114A, tubular portion 48 rotates clockwise, as long as the rider is activating switch 36, so that the front derailleur moves to the left. From step 114A, the system proceeds to step 115.

In step 115, the system checks to determine whether or not the right handlebar switch 34 has been activated. If the answer is no in step 115, indicating that the right handlebar switch is not activated, the system proceeds to step 116. On the other hand, if the answer is yes in step 115, the system proceeds to step 115A. In step 115A, the system activates actuator 24 to adjust the position of shift arm 12. In step 115A, tubular portion 48 rotates counterclockwise, as long as the rider is activating switch 34, so that the front derailleur moves to the right.

In step 116, a check is made to determine whether the set switch has been activated. If the answer is no in step 116, the system proceeds to step 120. If, on the other hand, the answer in step 116 is yes, indicating that the user has activated the set switch, the system proceeds to step 118.

In step 118, the system reads the position of the shift arms 12 and 10 from position sensors 16 and 14, the current cadence, and the current speed, and stores this information in the memory of data processing unit 32. From step 118, the system proceeds to step 120.

In step 120, the system checks whether the mode switch has been activated. If the answer is no in step 120, the system loops back to step 114 and processing continues as already previously described. The system remains in the front derailleur calibration mode until the user selects another mode by pressing the mode switch 86. On the other hand, if the answer in step 120 is yes, indicating that another mode has been selected, the system proceeds to step 122 and to the next mode in the sequence.

Reference is now made to FIG. 8, which figure illustrates the processing steps carried out by the system during the rear derailleur calibration mode. In this mode, the rider stores the correct positions of the rear derailleur for each gear position in the data processing unit's memory. In step 130, the system starts and proceeds to step 132 in which a check is made to determine whether or not the rear derailleur calibration mode has been selected. If the answer is no in step 132, the system continues in step 132 until the rear derailleur calibration mode is activated or some other mode of operation is selected by the rider. If, on the other hand, the answer is yes in step 132 indicating that the rider has selected the rear derailleur calibration mode, the system proceeds to step 134.

In step 134, the system checks to determine whether or not the left handlebar switch 36 has been activated. If the answer is no in step 134, indicating that the left handlebar switch is not activated, the system proceeds to step 135. On the other hand, if the answer is yes in step 134, the system proceeds to step 134A. In step 134A, the system activates actuator 22 to adjust the position of shift arm 10 which results in an adjustment to the position of the rear derailleur. In step 134A, tubular portion 48 rotates clockwise, as long as the rider is activating switch 36, so that the rear derailleur moves to the left. From step 134A, the system proceeds to step 135.

In step 135, the system checks to determine whether or not the right handlebar switch 34 has been activated. If the answer is no in step 135, indicating that the right handlebar switch is not activated, the system proceeds to step 136. On the other hand, if the answer is yes in step 135, the system proceeds to step 135A. In step 135A, the system activates actuator 22 to adjust the position of shift arm 10. In step 135A, tubular portion 46 rotates counterclockwise, as long as the rider is activating switch 34, so that the rear derailleur moves to the right. From step 135A, the system proceeds to step 136.

In step 136, a check is made to determine whether the set switch has been activated. If the answer is no in step 136, the system proceeds to step 140. If, on the other hand, the answer in step 136 is yes, indicating that the user has activated the set switch, the system proceeds to step 138.

In step 138, the system reads the position of the shift arms 12 and 10 from position sensors 16 and 14, the current cadence, and the current speed, and stores this information in the memory of data processing unit 32. From step 138, the system proceeds to step 140.

In step 140, the system checks whether the mode switch has been activated. If the answer is no in step 140, the system loops back to step 134 and processing continues as already previously described. The system remains in the rear derailleur calibration mode until the user selects another mode by pressing the mode switch 86. On the other hand, if the answer in step 140 is yes, indicating that another mode has been selected, the system proceeds to step 142 and to the next mode in the sequence.

When both the front and rear derailleur positions for each gear have been calibrated and stored in the system memory, the system can be operated in any one of the three operational modes; the manual mode, the semi automatic mode, or the fully automatic mode. When exiting the calibration modes, in steps 122 or 142, the system calculates gear ratios for all gear positions that have been set into memory, using cadence and speed data. The system calculates the gear ratio using the relationship: Gear ratio =wheel RPM/cadence The system then sorts the gear ratios and orders them from lowest to highest gear ratio.

Whenever the gears are thereafter shifted, the system automatically moves the front and rear derailleurs to the predetermined respective positions stored in the system memory for the selected gear using feedback control of the front and rear derailleur positions. The system eliminates minor adjustments to the position of the front derailleur (that have to be performed by the rider manually in conventional manual shifting systems) as the chain moves across the rear sprockets to automatically compensate for sharp chain angles between the front chainrings and the rear sprockets. Further, since the system has sorted and ordered the gear ratios, whenever the rider orders a shift using the handlebar switches, the system automatically selects the next numerically higher or lower gear ratio, regardless of the positions of the front and rear derailleurs.

The rider enters a cadence limit, which is used in the semi-automatic and fully automatic modes, by operating the system in the manual mode and shifting gears. The cadence limit used by the system in the semi automatic and fully automatic modes is the value of the cadence that the rider was using during his or her last shift while in the manual mode of operation.

Reference is now made to FIG. 9, which figure illustrates the processing steps carried out by the system in the semi-automatic mode of operation. In step 150, the system starts and proceeds to step 152 in which a check is made to determine whether or not the semi automatic operational mode has been selected. If the answer is no in step 152, the system waits until the semi automatic mode is activated or some other mode of operation is selected by the rider. If, on the other hand, the answer is yes in step 152 indicating that the rider has selected the semi-automatic mode, the system proceeds to step 154.

In step 154, the system calculates the theoretical cadence using the current gear ratio and bicycle speed data from wheel sensor 28. The calculated cadence is equal to the wheel RPM divided by the current gear ratio. (Gear ratio=wheel RPM/cadence.) From step 154, the system proceeds to step 156.

In step 156, the system determines whether or not the theoretical cadence calculated in step 154 is within the limits last set by the rider in the manual mode. If the answer is yes in step 156, then no change of gear ratio is required and the system proceeds to step 154 and processing continues as already previously described. On the other hand, if the answer in step 156 is no, indicating that the calculated cadence is outside the limits chosen by the rider in initializing step 152, the system proceeds to step 158.

In step 158, the system determines whether or not the cranks are turning, i.e., whether or not the rider is pedaling, by checking the signal from the cadence sensor 26. If the system determines that the cranks are not turning, as may be the case when the rider is gliding, for example, the system proceeds to step 154 and processing continues as already previously described. On the other hand, if the system determines that the cranks are turning, i.e., that the rider is pedaling, the system proceeds to step 160.

In step 160, the system checks to determine whether the calculated cadence is too low. If the answer in step 160 is no, indicating that the cadence is outside the rider's selected limits and is not too low (indicating that the rider's cadence is too high), the system proceeds to step 162. In step 162 an upshift signal, which may be a visual signal on display 82 and/or an audio signal such as two successive beeps is sent to the rider which informs the rider that to maintain his or her cadence within the preprogrammed limits, an upshift is desirable. If the rider decides to upshift, he or she presses handlebar switch 34. From step 162 the system proceeds to step 166.

Returning to step 160, if the system determines that the calculated cadence is outside the rider's selected limits and is too low (indicating that the rider's cadence is too low), the system proceeds to step 164. In step 164, a downshift signal, which may be a visual signal on display 82 and/or an audio signal such as a single beep, is sent to the rider which informs the rider that to maintain his or her cadence within the preprogrammed limits, a downshift is desirable. If the rider decides to downshift, he or she presses handlebar switch 36. From step 164, the system proceeds to step 166.

In step 166, the system checks to determine whether the mode switch has been activated. If the answer is no in step 166, the system proceeds to step 154 and processing continues as already previously described. The system remains in the semi automatic mode until another mode is selected by the rider. On the other hand, if the system determines in step 166 that the mode switch has been activated, the system proceeds to step 168. In step 168, the system proceeds to the next mode in the sequence.

Reference is now made to FIG. 10, which figure illustrates the processing steps carried out by the system when in the fully automatic mode of operation. In step 200, the system starts and proceeds to step 202 in which a check is made to determine whether or not the fully automatic operational mode has been selected. If the answer is no in step 202, the system waits until the fully automatic mode is activated or some other mode of operation is selected by the rider. If, on the other hand, the answer is yes in step 202 indicating that the rider has selected the fully automatic mode, the system proceeds to step 204.

In step 204, the system calculates the theoretical cadence given the current gear ratio and bicycle speed data from wheel sensor 28. The calculated wheel RPM divided by the cadence is equal to the current gear ratio. (Gear ratio=wheel RPM/cadence.) From step 204, the system proceeds to step 206.

In step 206, the system determines whether or not the theoretical cadence calculated in step 204 is within the limits last set by the rider in the manual mode. If the answer is yes in step 206, then no change of gear ratio is required and the system proceeds to step 204 and processing continues as already previously described. On the other hand, if the answer in step 206 is no, indicating that the calculated cadence is outside the limits chosen by the rider in initializing step 202, the system proceeds to step 208.

In step 208, the system determines whether or not the cranks are turning, i.e., whether or not the rider is pedaling, by checking the signal from the cadence sensor 26. If the system determines that the cranks are not turning, as may be the case when the rider is gliding, for example, the system proceeds to step 204 and processing continues as already previously described. On the other hand, if the system determines that the cranks are turning, i.e., that the rider is pedaling, the system proceeds to step 210.

In step 210, the system checks to determine whether the calculated cadence is too low. If the answer in step 120 is no, indicating that the cadence is outside the rider's selected limits and is not too low (indicating that the rider s cadence is too high), the system proceeds to step 212. In step 212, an upshift signal, which may be a visual signal on display 82 and/or an audio signal such as two successive beeps is sent to the rider which informs the rider that to maintain his or her cadence within the preprogrammed limits, an upshift is to occur. From step 212, the system proceeds to step 214.

In step 214, the system pauses for a fixed amount of time, such as one second. It has been found that some bicycle transmission systems shift better when the rider reduces the torque on the gears during a shifting operation. Therefore, step 214 allows a predetermined pause so that the rider may ease up on the pedals before the shift occurs. From step 214, the system proceeds to step 216.

In step 216, an upshift operation is performed. The upshift operation automatically, and without any action on the part of the rider, shifts the bicycle gears into the next higher gear ratio, which effectively reduces the rider s cadence. From step 216, the system proceeds to step 224.

Returning to step 210, if the system determines that the calculated cadence is outside the rider s selected limits and is too low (indicating that the rider's cadence is too low), the system proceeds to step 218. In step 218, a downshift signal, which may be a visual signal on display 82 and/or an audio signal such as a single beep, is sent to the rider which informs the rider that to maintain his or her cadence within the preprogrammed limits, a downshift is to occur. From step 218, the system proceeds to step 220.

In step 220, the system pauses for a predetermined interval of time in order to allow the rider to ease up on the pedals for those bicycle shifting systems that perform better under reduced pedal pressure. From step 220, the system proceeds to step 222.

In step 222, a downshift operation is performed. During the downshift operation, the electronic control system automatically, and without any action by the rider, moves the bicycle s derailleurs so as to downshift the bicycle by one gear, effectively increasing the gear ratio and increasing the rider's cadence. From step 222, the system proceeds to step 224.

In step 224, the system checks to determine whether the mode switch has been activated. If the answer is no in step 224, the system proceeds to step 204 and processing continues as already previously described. The system remains in the fully automatic mode until another mode is selected by the rider. On the other hand, if the system determines in step 224 that the mode switch has been activated, the system proceeds to step 226. In step 226, the system proceeds to the next mode in the sequence.

The electronic bicycle transmission control system of the present invention allows fully automatic control over gear shifting operations while improving the rider s efficiency as well as safety. The control system is retrofittable to a wide range of conventional bicycles and adds less than two pounds to the weight of the bicycle and therefore does not adversely affect the weight or handling characteristics of the bicycle. In addition, the system is able to complete a gear shift operation in approximately one second. This shift time is usually faster than a rider is able to achieve manually as well as being more accurate because the correct positions for the derailleurs for each gear have already been stored in the system memory.

Having thus described one particular embodiment of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. For example, it will be appreciated that the present invention is not limited solely to ten speed type bicycles but may in fact be retrofitted on a variety of multi gear type bicycles such as 15, 20 or even 24 speed bicycles.

One skilled in the art will also realize that the present invention can be integrated into the bicycle itself. Motors, sensors, batteries, and switches can be designed into the frame of the bicycle, thereby decreasing system weight and wind resistance. Furthermore, the handlebar mounted switches could be replaced with voice activated sensors using voice recognition electronics.

Additionally, features of current bicycle computers, including torque measurement for calculation of work output, altimeter functions, heart rate monitoring, downloading data to a computer for displaying and recording the rider s performance, and other features can all be incorporated into the present invention. Some of these capabilities, when added to the present invention, form the basis for an expert system for determining when to shift gears for optimum performance and efficiency. For example, expert system software could learn how a particular rider's power output varies as a function of altitude, heart rate, and cadence, and then control the gear ratio selection accordingly.

One skilled in the art will further appreciate that the present invention is not limited to bicycle applications only, but may be retrofitted on a wide variety of human-powered vehicles. Such alterations, modifications, and improvements as are made obvious by this disclosure are intended to be part of this disclosure though not expressly stated herein, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention is limited only as defined in the following claims and the equivalents thereto. 

What is claimed is:
 1. A bicycle transmission control system, comprising:generating means responsive to a rider for generating torque; transmitting means for transmitting torque from the generating means to at least one wheel of the bicycle; determining means for determining a cadence of the generating means in response to a calculated gear ratio and sensed bicycle speed; means for indicating if the cadence determined by the determining means is outside a predetermined range for the calculated gear ratio and sensed bicycle speed; and means for adjusting the transmitting means if the cadence determined by the determining means is outside the predetermined range for the calculated gear ratio and sensed bicycle speed
 2. The control system of claim 1 wherein the adjusting means further comprises actuation means including motor means.
 3. The control system of claim 2 further comprising shaft arm means coupled to and controlled by the said actuation means.
 4. The control system of claim 3 wherein the determining means includes control means comprising digital data processing means.
 5. The control system of claim 4 further comprising calibration means including memory means for determining and storing a state of the adjusting means for each gear ratio.
 6. The control system of claim 5, wherein the transmitting means includes first and second sets of gears and an endless chain coupling between the first and second sets of gears.
 7. The control system of claim 6 further comprising first and second derailleurs for positioning the endless chain on selected gears in the first and second sets of gears.
 8. The control system of claim 7 wherein the actuation means includes first and second actuators and the shift arm means includes first and second shift arms respectively coupled to the first and second actuators.
 9. The control system of claim 8 wherein the control means includes means for independently selecting a respective position of the first and second derailleurs to compensate for an angle of the endless chain coupling between the first and second sets of gears.
 10. The control system of claim 9 wherein the first and second sets of gears each include a plurality of coaxially mounted gears.
 11. The control system of claim 10 wherein the coaxially mounted gears in the first or second set of gears are uniformly spaced from one another.
 12. The control system of claim 11 wherein the coaxially mounted gears in the first or second set of gears are nonuniformly spaced from one another.
 13. A bicycle including a frame, a set of gears, a derailleur controlled by a shift cable for selecting one of the gears, and having a retrofittable derailleur control system installed on the bicycle comprising an electro-mechanical actuation means including a rotating tubular portion having an inner threaded periphery attached to the frame, a shift arm means pivotally attached to the frame and coupled to the actuation means so that the shift arm means, in response to movement of the actuation means, acts on the shift cable to control the derailleur to select one of the gears.
 14. The retrofittable control system of claim 13 further comprising a threaded shaft having two ends, one end engaging the inner threaded periphery and the other end pivotally coupled to the shift arm means.
 15. The retrofittable control system of claim 14 wherein the shift arm means comprises a bellcrank means having a planar configuration.
 16. The retrofittable control system of claim 15 wherein the bellcrank means includes an actuation point which engages the shift cable.
 17. The retrofittable control system of claim 16 wherein the actuation point slidably engages the shift cable.
 18. A method for controlling gear changing in a bicycle transmission comprising the steps of:calibrating the bicycle transmission by calculating a gear ratio from sensed bicycle speed and sensed cadence for each position of a derailleur in the bicycle transmission during a calibration mode; sorting the calculated gear ratios during the calibration mode; calculating a theoretical cadence from sensed bicycle speed and calculated gear ratio during an operational mode; determining if the calculated theoretical cadence is within predetermined limits; and providing a signal if the calculated theoretical cadence is outside the predetermined limits.
 19. The method of claim 18 further comprising a step of changing gear ratios in response to the provided signal.
 20. The method of claim 19 wherein the step of changing gear ratios further comprises decreasing a gear ratio if the calculated cadence is below a lower predetermined limit.
 21. The method of claim 19 wherein the step of changing gear ratios further comprises increasing the gear ratio if the calculated cadence is above an upper predetermined limit.
 22. The method of claim 18 wherein the step of signaling includes providing a first signal if the calculated cadence is below a lower predetermined limit and a second signal if the calculated cadence is above an upper predetermined limit.
 23. The method of claim 19 further comprising a step of storing a state of the transmission for each gear ratio.
 24. The method of claim 23 wherein the step of storing a state of the transmission includes storing at least one position of at least one derailleur in the transmission.
 25. A transmission control system for a human-powered vehicle, comprising:a gear means; a crank means coupled to the gear means; cadence determining means for determining a cadence of the crank means; adjusting means including at least one actuator comprising motor means and at least one bellcrank pivotally coupled to and controlled by the at least one actuator; and computer control means responsive to the cadence determining means, for controlling the adjusting means, the computer control means comprising means for comparing the cadence with predetermined limits, means responsive to the comparison means for controlling the adjusting means, and at least one gear position sensor.
 26. The transmission control system of claim 25, further comprising means for sensing bicycle speed.
 27. The transmission control system of claim 26, wherein the computer control means includes means for calculating a gear ratio based on sensed bicycle speed and the cadence determined by the cadence determining means for each position of the derailleur means.
 28. The transmission control system of claim 27 wherein the control means includes means for sorting gear ratios calculated by the calculation means.
 29. The control system of claim 25 further comprising at least one switch means for directing the computer means to adjust the gear means.
 30. A bicycle transmission control system, comprising:a derailleur means for moving a chain between gears; means for sensing a position of the derailleur means; means for sensing bicycle speed; means for sensing a cadence; and control means, responsive to the means for sensing a position of the derailleur means, the control means comprising calculation means for calculating a gear ratio in response to sensed bicycle speed and sensed cadence for each position of the derailleur means, for controlling the position of the derailleur means.
 31. The bicycle transmission control system of claim 30 further comprising actuation means coupled to the derailleur means and responsive to the control means, for changing the position of the derailleur means.
 32. The bicycle transmission control system of claim 31 further comprising switch means for signaling the control means to change the position of the derailleur means.
 33. The bicycle transmission control system of claim 30 wherein the control means includes means for sorting gear ratios calculated by the calculation means.
 34. In a bicycle having at least one set of sprockets coupled to at least one wheel and a chain which is selectably moved between individual sprockets int he set of sprockets by an adjusting means, a programmable, retrofittable control system, comprising:switch means for entering data relating to at least a physical configuration of the at least one set of sprockets; reprogrammable memory means for storing the data relating to at least the physical configuration of the at least one set of sprockets and data relating to a state of the adjusting means for any selected individual sprocket in the set of sprockets; accessing means for retrieving the data stored in the memory means; means for receiving commands from a rider, the commands indicating a desired position of the adjusting means; and control means, responsive to the means for receiving command and the data retrieved by the accessing means, for controlling the adjusting means to move the chain to any selected individual sprocket in the set of sprockets.
 35. The programmable, retrofittable control system of claim 34 wherein the control means further comprises position sensing means, coupled to the adjusting means, for providing a signal representative of a position of the adjusting means.
 36. The programmable, retrofittable control system of claim 35 wherein the control means further comprises means, responsive to the position sensing means for signalling the control means when the adjusting means has reached a selected position corresponding to a selected individual sprocket in the set of sprockets.
 37. The programmable, retrofittable control system of claim 34 wherein the memory means stores a cadence of the rider.
 38. The programmable, retrofittable control system of claim 34 wherein the memory means stores at least one calculated gear ratio.
 39. The programmable, retrofittable control system of claim 35 wherein the memory means stores a plurality of calculated gear ratios.
 40. The The programmable, retrofittable control system of claim 34 wherein the memory means stores a set of calculated gear ratios ordered from highest to lowest gear ratio. 